I am running Memtest86+ v.4.20 and noticed what are shown for the Settings are incorrect. The CPU die size as 65nm is also incorrect. The RAM in use is a pair of 4GB DDR3-1600 CAS 9-9-9-24. The screen shot of the Memetest86+ is as follows. What could be wrong?

Because RAM is a funny beast and some errors don't manifest unless you let the test run a long, long time. You're free to stop the tester, but you could also let it run overnight and be a bit more sure that your RAM is good.

OTOH I've had a few times when RAM was definitely bad but the tester didn't pick up on it, but the computer worked fine once the offending stick was replaced.

bthylafh wrote:Because RAM is a funny beast and some errors don't manifest unless you let the test run a long, long time. You're free to stop the tester, but you could also let it run overnight and be a bit more sure that your RAM is good.

Does the second pass and thereafter repeat the exact same test as the first pass?

OTOH I've had a few times when RAM was definitely bad but the tester didn't pick up on it, but the computer worked fine once the offending stick was replaced.

Some of the tests are identical, some are changed randomly with each pass. Also, RAM failures tend to be intermittent. In order to find an intermittent problem, you need to run the same tests over and over again until the intermittent problem occurs.

RAM chips consist of a large array of tightly packed memory cells, one for each bit of data. The vast majority of the intermittent failures are a result of interaction between these memory cells. Often writing a memory cell can cause one of the adjacent cells to be written with the same data. An effective memory test attempts to test for this condition. Therefore, an ideal strategy for testing memory would be the following:

nerdrage wrote:Some of the tests are identical, some are changed randomly with each pass. Also, RAM failures tend to be intermittent. In order to find an intermittent problem, you need to run the same tests over and over again until the intermittent problem occurs.

RAM chips consist of a large array of tightly packed memory cells, one for each bit of data. The vast majority of the intermittent failures are a result of interaction between these memory cells. Often writing a memory cell can cause one of the adjacent cells to be written with the same data. An effective memory test attempts to test for this condition. Therefore, an ideal strategy for testing memory would be the following:

While straight up defective chips should be detected with a single pass, chips with impurities that leave them functional, but effect performance have other considerations.Transistors in memory chips (and all digital silicon chips for that matter) have rise and fall times that vary with environmental considerations such as voltage and heat.

Heat causes physical expansions in the silicon that, while microscopic, are significant when compared to the size of the transistor. If you have a chip that is already marginal, then even adding a small increase to the path length through a transistor can push it over the top. The actual amount of expansion is different between cases and obviously depends on your cooling solution, but it only takes one transistor missing timing to make your memory bad. So you must wait for them system to warm up before you can call it good.

The voltage supplied to the gate of the transistor also effects how quickly the transistor switches. Higher voltages turn on (or shut off) a transistor more quickly (hence its use in overclocking), but also increase power loss and heat dissipation. If a memory chip is marginal, a small droop in voltage at the wrong time can cause failures. Lower quality DC regulation in power supplies or in the voltage regulator modules on a motherboard can cause such droops. While these droops may occur with some low frequency, it is only when the transistor(s) in question are being accessed that such a droop will actually cause a failure. The length of time you must run the test to catch such an error depends on the frequency of droops and the probability that they occur when the marginal transistor is in use. The droops can also be cause by transients such as a large, sudden increase in power draw from events like spinning up a large array of HDDs all at once or suddenly going from a near power off state to full load with a (or several) high powered graphics card. A similar issue can crop up if voltages spike during access. Memory cells are tightly packed and a relative spike into one memory cell can bleed into surrounding cells potentially turning them on if they were off. Even an overclock on your processor can effect it. Though to be fair, power supplies and motherboards with good transient responses will go a long way to resolving such issues. These transient issues are often missed by dedicated memtesters as they require system loading not present in the memtester environment to cause the error. I agree with the overnight suggestion above as it is increasingly improbable that any issues not seen in that time frame will be seen by the dedicated memtester at all. Some of the 3DMarks benchmarks have shown themselves to be quite sensitive to overclocking issues, so that is another tool you can use, but they don't really use that much RAM.

Most memory errors where the chip isn't flat out defective (and thus generally easily detectible) are a combination of the above heating and voltage regulation issues on marginal chips. It follows that an increase in voltage, a decrease in timings, or a decrease in clock speed will often times resolve these marginal issues. Just keep in mind that you don't always have the ability to modify the part of the chip that is effected, though there are plenty of motherboards that expose the vast majority of these settings.

Same test algorithms, but IIRC some of the sub-tests use pseudo-random numbers which will change with each pass.

As others have noted, RAM failures are often intermittent in nature. IMO the best way to use Memtest86 is to launch it before you go to bed (or before you leave for work), and let it run multiple passes over several hours when you don't need to use the PC.

I can share my own anecdotal experience: I once had a pair of new RAM sticks and memtest failed on pass #20 out of #23, at around the 13 hour mark. Due to different access patterns, in regular use it may show up sooner. Plus, I was going to overclock so I need the RAM to have a smaller margin of error. Since the sticks were new, so I could return the kit and got a new set and not needed to bother with isolating which stick.

The Model M is not for the faint of heart. You either like them or hate them.

If still interested Memtest86+ 5.00 is available in the "reviewer Kit for Intel Haswell" from http://www.cpuid.com/

From the readme;

The long-awaited Memtest86+ 5 is finally here !

For reviewers, here are some tips :

- Press F1 at startup to enable "Safe Mode". Could be useful if you're reviewing an A-Step HSW or an early engineering-sample of a GT3e-enabled CPU.

- Press F2 to toggle the experimental SMT support in case of any problem. SMT is disabled by default on all Xeon/Opteron and any Engineering Sample CPU. You can press F2 to force SMT, but nothing guaranteed !

- [Hidden Mode] Press F3 to enable an alternative way to detect SMT. Only useful on Gigabyte Motherboard at this time.

Note about SMT : our internal tests showed that SMT only speed up the tests but DO NOT help in finding more errors.